With regard to lithium secondary batteries in which graphite is used, there are a number of patent applications, including Japanese Unexamined Patent Publication No.57-208079 (Japanese Examined Patent Publication No.62-23433). However, the theoretical capacity of graphite as calculated from the composition LiC.sub.6 is considered 372 Ah/kg (carbon basis). The theoretical capacity of graphite as a host for lithium is also 372 Ah/kg (carbon basis). Thus, there has been a limit to discharge capacity.
However, the electronic device industry uninterruptedly demands conspicuous improvements in battery performance. To meet the requirements for high performance battery, significant improvements in the properties of the negative electrode to be used in the lithium secondary battery are essential. In view of the situation, the capacity of 372 Ah/kg cannot be considered sufficiently high in terms of negative electrode capacity.
Therefore, the modification of graphite-based intercalation compound heretofore-proposed is not enough to attain the needed lithium storage capacity.
The object of the present invention, in consideration of the above state of the art, is to provide a lithium secondary battery having a charge/discharge capacity exceeding the theoretical capacity of 372 Ah/kg and to provide negative electrode useful in the a lithium secondary battery, a negative electrode material, and a process for preparing a carbon material therefor.